Non-woven inorganic fiber mat

Abstract

A non-woven mat of inorganic fiber is disclosed having a substance which is lower at the edges of the mat than in the remainder of the mat. Apparatus for making such a mat includes: a source of a slurry of inorganic fiber in a liquid; a forming wire disposed to move past the source, the liquid passing through the forming wire to deposit the inorganic fiber on the forming wire; a mask across a part of the width of the forming wire to hinder passage of the liquid through the forming wire over the part, the effectiveness of the mask varying in the direction of movement of the forming wire past the slurry source. A method of making the mat includes passing a forming wire past a slurry of inorganic fibers in a liquid while masking a part of the width of the forming wire as it passes through the slurry, the masking varying along the length of the forming wire as it passes through the slurry; and urging the slurry against the forming wire and causing the liquid to pass through the forming wire, whereby a non-woven mat of inorganic fiber is formed having an uneven substance (weight/unit area) in the cross direction.

The invention claimed is: 
     
       1. A non-woven mat of glass fiber, comprising:
 said mat having a substance weight/unit area varying in a cross direction; and 
 at least one edge margin of said mat is of lower substance weight/unit area than the remainder of said mat, 
 wherein the substance weight/unit area of the at least one edge margin is generally uniform across an entire width of the at least one edge margin, and said mat is permeable to a gypsum plaster slurry. 
 
     
     
       2. The mat according to  claim 1 , wherein opposed edge margins of said mat are of lower substance weight/unit area than the remainder of said mat. 
     
     
       3. A cementitious board having a sheet of a non-woven mat of glass fiber according to  claim 1  embedded immediately below at least one surface thereof. 
     
     
       4. A cementitious board having a sheet of a non-woven mat of glass fiber according to  claim 2  embedded immediately below at least one surface thereof. 
     
     
       5. The mat according to  claim 1 , wherein said mat is made of a single layer of non-woven glass fiber. 
     
     
       6. The mat according to  claim 2 , wherein said mat is made of a single layer of non-woven glass fiber. 
     
     
       7. A cementitious board having a sheet of a non-woven mat of glass fiber according to  claim 5  embedded immediately below at least one surface thereof. 
     
     
       8. A cementitious board, comprising:
 a body of cementitious material; and 
 a non-woven mat of glass fiber embedded immediately below at least one surface of said body, said mat having a substance weight/unit area varying in a cross direction, and at least one edge margin of said mat is of lower substance weight/unit area than the remainder of said mat, 
 wherein the substance weight/unit area of the at least one edge margin is generally uniform across an entire width of the at least one edge margin, and said mat is permeable to a gypsum plaster slurry. 
 
     
     
       9. The cementitious board according to  claim 8 , wherein opposed edge margins of said mat are of lower substance weight/unit area than the remainder of said mat. 
     
     
       10. The cementitious board according to  claim 8 , wherein said mat is made of a single layer of non-woven glass fiber. 
     
     
       11. The cementitious board according to  claim 9 , wherein said mat is made of a single layer of non-woven glass fiber.